UBVRI light curves of ER Vul

New photoelectric UBV and BVRI observations, secured during August-November of 2002 at two observatories distant in local time are analyzed together with two earlier photometric data sets and all available radial velocities to derive the most accurate ephemeris of the binary and to set limits on its basic physical elements. These observations were obtained as a support for a high-dispersion spectroscopic study, results of which will be published separately.

It was found that radial velocities and photometric observations spanning 53 years can be reconciled with the linear ephemeris T_(prim.min.)_=HJD 2440182.25628(46) + 0.698095113(29)days x E, where the rms errors of the last digits are given in brackets. Masses of the stars are 1.02 and 0.97 solar masses and the binary separation is 4.170 solar radii. There is still a large uncertainty in the stellar radii.